I
thought I had seen a set just like this or at least very similar when I
came up with this set, but looking over the site I couldn't find it, so
here it goes:

We
did this with our top middle schoolers (11-14). We swim SCM, and
intervals listed are for our top group. The set was adapted all the way
down to 6 different intervals and distances (although this group
probably got the most amount of rest, since they can respond to it with
faster swims).

Goal
was to swim the 50s really efficient, and work the IM transitions from
flags in to the breakout, then hit the longer IMs. We had plenty of
great swims through the set, and by the end the kids threw down some
of their best ever practice 400IM times!